Compensated transformer



Sept. 22, 1959 w. T. HARRIS 2,905,915

coMPENsATED TRANSFORMER Original Filed Jan. 22, 1954 FIG. 2.

INVENTOR. W/LBUA 7,' HARK/5 BY l United States Patent O ce CMIENSATED TRANSFORMER Wilbur T. Harris, Southbury, Conn., assignor to The Harris Transducer Corporation, Woodbury, Conn., a corporation of Connecticut Original application January 22, 1954, Serial No. 405,614, now Patent No. 2,776,416, dated January 1, 1957. Divided and this application July 13, 1955, Serial No. 521,745

13 Claims. (Cl. 336-181) My invention relates to an improved core and Winding construction for electromagnetic circuit elements, and this application is concerned particularly with transformer embodiments of said invention. This application is a continuation-in-part of my application Serial No. 318,720, filed November 4, 1952 (now Patent No. 2,776,417), and is a division of my application Serial No. 405,614, filed January 22, 1954 (now Patent No. 2,776,416).

It is an object of the invention to provide improved devices of the character indicated.

It is a specific object to provide an improved transformer core and winding construction having the basic virtues of toroidally wound cores, without requiring the elaborate fabrication techniques necessary with toroidal windings.

It is another specific object to provide an improved transformer construction in which stray hum or other pick-up may be completely and inherently compensated for and, therefore, neutralized.

Other objects and various further features of novelty and invention will be pointed out or will occur to those skilled in the art from a reading of the following specilication in conjunction with the accompanying drawings. In said drawings, which show, for illustrative purposes only, preferred forms of the invention:

Fig. 1 is a simplified longitudinal sectional View through a transformer incorporating features of the invention; and

Figs. 2, 3, and 4 are similar Views of further embodiments.

Briey stated, my invention contemplates a new core and winding construction employing what may be termed a toroidal magnetic core, thereby providing a generally toroidal iiux path. In application to transformers, input and output helical-signal windings are coupled to the core path and to the stray-linx path, and compensating windings are coupled to the stray-flux path to the exclusion of or effectively independently of the core path. The compensating windings are differentially connected to their respective signal-winding counterparts and have substantially the same number of turns, so that any coupling to the stray-flux path (whether it be in the input or primary circuit, or in the output or secondary circuit) will be completely neutralized, and coupling by Way of the core will, in effect, be exclusively promoted. In. one general form, represented by Figs. 1 and 3, the compensating windings are physically located radially inside the signal windings. In the other general form, represented by Figs.y 2 and '4, the compensating windings are physically located radially outside the toroidal'ux path andv therefore, radially outside the signal windings.

Referring to Fig. l of the drawings, my invention is shown in application to a transformer having electrically independent input and output circuit connections -11 for an input winding 12 and an output winding 13. The windings 1213 are coupled to each other solely by Way o flthellux path circulating in the core, and in accordance Patented Sept. 22, 1959 with the invention, said flux path is toroidal. The toroidal dlux path may be established by elements of magnetic ma terial and is shown to utilize an inner elongated cylinder 14, an outer elongated cylinder 15, and two end-closure plates 16-17. The cylindrical members 14-15 may be of magnetic-oxide ceramic, but are shown sectioned for metal and may simply be helically developed laminated tubes of transformer iron. The end caps 16-17 are shown as of magnetic oxide ceramic and may be bonded to the tubes 14-15.

The windings 12-13 are developed over the inner tubular core member 14 and are therefore electromagnetically coupled thereto so that, upon application of a signal or voltage at the input 10, flux is caused to circulate toroidally. By toroidal llux circulation, I mean that for a voltage of instantaneous direction determining ilux say, from left to right along the inner core member 14, said flux also circulates radially outwardly in the end-closure member 17, from right to left in the outer tubular member 15, and radially inwardly in the end-closure member 16. For voltage of reversed instantaneous polarity, the described toroidal flux is in the reverse directional sense.

Although the windings 12-13 are directly coupled to the toroidal flux path, it is also a fact that they are coupled to any stray flux in which the described device may happen to be immersed, and of course for such stray flux, voltages will be induced so as to alter the effective signal transfer between input and output circuits 10-11. In accordance with the invention, I effectively neutralize such stray-flux effects by providing additional or compensating windings 18-19 having substantially the same number of turns as their signal-winding counterparts 12-13 and disposed for essentially the same coupling to the stray flux, to the exclusion of the toroidally circulated flux in the core. Thus, the winding 18 may be differentially connected to the winding 12 so that signal input at 10 is effectively applied to windings 12-18 in series opposition; thus, the axially inner ends of windings 12-18 may be directly connected, as through the hole shown in core 14, so that a compensated input circuit is presented at 10. In the same manner, the windings 13-19 are differentially connected, and voltage output at 11 reflects the series opposition of windings 13-19; this connection may involve the axially inner ends of windings 13-19, as explained for windings 12-18.

The arrangement of Fig. 2 incorporates essentially the same principles as those described for Fig. l, except for the fact that the compensating windings 18-19 are disposed radially outside, rather than inside, the signal windings 12-13. Thus, the windings 18-19 may be developed on the periphery of the outer tubular core member 15, and the inner core member 14 need not be tubular. The dotted interconnections of windings 12'- 18' and 13-19 involved passage of wire through suitable holes (not shown) in core member 15, as for the case of core member 14 in Fig. l. As explained in connection ywith Fig. l, the core members 14--15 may be of magnetic oxide ceramic, as is the case for the endclosure members 16-17. It will be appreciated that in Fig. 2 any coupling ofwinding 18 or of winding 19 to the core is, in effect, neutralized so that windings 18'-- .the inner core member 14', radially outwardly directed flux in the end-closure member 17, flux from right to left in the outer core member 15, and radially inwardly directed flux in the end-closure member 16. For the;l samey voltage, any iiux developed. theA `compensating wind-ing 18 in the core member 15 will be equally and oppositely opposed by uX similarly developed in the core member 14 so that the winding 18,' (and, by the same token, winding 19') cannotaccount for netA ux development in the core.

Thearrangements of Figs. 3 and 4 incorporate princi` ples discussed in connection with Figs. l and 2 except that the application is to an auto-transformer, rather than to a transformer with electrically independent input and output circuit connections. The core of Fig. 3 may be the same as the core of Fig. l and, therefore, the same reference' numerals have been employed; likewise, for Fig. 4, the core numerals follow those' used in Fig. 2. In Fig. 3, a single signal winding 2t) is developed over the inner core member 14, andthe input circuit 21 is connected to a fraction of the total number of turns of the winding 20. Since the stray-fluxl coupling v'due to winding 20 is determined by the number of turns and not necessarily by the input circuit connection, it is merely necessary to employ a single compensating winding 22 differentially connected to the winding 20 at 23, so that the output at 24 reects differential combination of voltages induced in the winding 20 and inv the winding 22.

The electrical connections in Fig. 4 are essentially the same as those described in Fig. 3, so that primed notation is employed. The only difference is that stray-ilux compensation voltages are developed by winding 22' externally of the signal Winding 20' rather than radially in- Wardlythercof as in the case of Fig. 3.

It will be appreciated that I have described relatively simple winding and core constructions lending themselves to mass-production techniques which are already well understood and for which there is a relative abundance of machinery. Every winding described may be developed as a pure helical progression, from Wire available on a reel, and without requiring special techniques as is custom-V ary with toroidal winding. My construction nevertheless has the inherent advantage of a toroidal Winding, in that susceptibility to stray ux (which would otherwise be characteristic of a helically wound construction) is reduced to substantially zero. While it has been possible in the past to avoid these undersirable characteristics by resorting to complex fabrication methods and expensive machinery to create toroidal windings, my construction avoids the need for such complexity and expense.

While I have described the invention in detail for the preferred forms shown, it will be understood that modifications may be made within the scope of the invention as defined in the claims which follow.

I claim:

l. A transformer, comprising magnetic-core means establishing a continuous toroidal flux path; input-winding means including a first winding linked to said iiux path and to the stray-ux path through the center of said toroidal path, and a compensating winding differentially connected to said first winding and linked to said strayflux path to the exclusion of said first-mentioned iiux path; and output-winding means including a second winding linked to said first-mentioned flux path and also to said strayiflux path, and a further compensating winding differentially connected to said second winding and linked to said stray-linx path 'to the exclusion of said rstwmentioned iiuxpath.

2.. A transformeraccording to claimV l, in which said twoiirst-mentioned windings have substantially the same number of turns.

3. A transformer according to claim l, in which said two last-mentionedwindings have substantially the Same number of turns.

4. A circuit element according to claim l, in which the number of turns of said input-winding means is different from thenumber of turns of said output-winding means.

51 In a'device'of the character indicated, two 'elongatedl 4 generally cylindrical members of magnetic material one within the other and magnetically interconnected at their corresponding ends, whereby a generally toroidal ux path is thereby defined, a first winding in the radial space between said members and therefore coupled to said flux path, a second winding developed along and radially within the inner of said members and therefore not coupled to said iluX path, an electrical autotransformer'tap connection to an intermediate part of said first winding, and means electrically diierent-ially connecting said' second winding in series with one of the ends of said first4 winding.

6. In a device of lthe character indicated, two elongated generally cylindrical members of magnetic material one within the other and magnetically interconnected at' their corresponding ends, whereby a generally toroidal flux path is thereby defined, a first winding in the radial space between said members and therefore coupled to said flux path, a second winding developed along and radially outside the outer of said members and therefore not coupled to said flux path, an electrical autotransf'ormer tap connection to an intermediate part of said rst Winding, and' means electrically differentially connecting said second winding in series with one of the ends of said rst winding.l

7. In a device of the character indicated, a core com.- prising two elongated cylindrical' members Vof magnetic 4 material one radially spaced within the other and magnetically interconnected at their corresponding ends, first winding means in the radial space between said membersand therefore coupled to said core, said rst winding means comprising separate sets of turns constituting primary and secondary halves of a transformer, second Wind ing means substantially axially coextensive with said first winding means but independent of effective coupling to said core, and means electrically diierentially interconnecting said winding means, whereby stray-field effects common to both winding means may be substantially eliminated.

8. A device according to claim 7, in which said separate sets of turns are electrically independent of each other. f

9. A device according to claim 7, in which said separate sets of turns are separate parts of the same single winding.

l0. In a circuit element of the character indicated, ar core-body defining a continuous toroidal magnetic-core path; first winding means including a rst winding linked to said core path and to the stray-flux path in which said circuit element may be immersed, and a second Winding differentially connected to said first Winding; and second Winding means including a' third winding linked to` said core path and also to said stray-flux path, and a fourth winding differentially connected to said third winding; said second and fourth windings being unenclosed by the torus of said path and therefore linked to the stray-linx path to the exclusion of said core path.

l1. A circuit element according to claim l0, in which said first and second windings have substantially the same number of turns.

12. A circuit elementA accordingto claim l0, in which the number of turns of said rst winding means is dieri ent from the number of turns of said second winding means, whereby a transformer action is achieved between said Winding means. l l l 13. A circuit element according to claim 10,'1n whlc'h' said second and. fourth windings are, radially'outside'saidlcore path..

References Cited in the tile of this patent.V

UNITED STATES PATENTS Aigr- 

